U.S. patent application number 14/449711 was filed with the patent office on 2015-02-19 for electrochemical reduction method of carbon dioxide using solution containing potassium sulfate.
The applicant listed for this patent is KC Cottrell Co., Ltd., Korea South Power Co., Ltd., Sogang University Research Foundation. Invention is credited to Gwang Gyu Kim, Suk Kyu Kim, Ki Nam Kwon, Kye Yun Lee, Sae Young Oh, Mi Jung Park, Woonsup Shin, Chan Hyo Yu.
Application Number | 20150047986 14/449711 |
Document ID | / |
Family ID | 50648216 |
Filed Date | 2015-02-19 |
United States Patent
Application |
20150047986 |
Kind Code |
A1 |
Shin; Woonsup ; et
al. |
February 19, 2015 |
ELECTROCHEMICAL REDUCTION METHOD OF CARBON DIOXIDE USING SOLUTION
CONTAINING POTASSIUM SULFATE
Abstract
The embodiments described herein pertain generally to an
electrochemical reduction method of carbon dioxide under a solution
condition containing potassium sulfate.
Inventors: |
Shin; Woonsup; (Seoul,
KR) ; Oh; Sae Young; (Seoul, KR) ; Kim; Suk
Kyu; (Guri-si, KR) ; Park; Mi Jung; (Seoul,
KR) ; Kwon; Ki Nam; (Yongin-si, KR) ; Yu; Chan
Hyo; (Seoul, KR) ; Kim; Gwang Gyu; (Seoul,
KR) ; Lee; Kye Yun; (Gwacheon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sogang University Research Foundation
KC Cottrell Co., Ltd.
Korea South Power Co., Ltd. |
Seoul
Seoul
Seoul |
|
KR
KR
KR |
|
|
Family ID: |
50648216 |
Appl. No.: |
14/449711 |
Filed: |
August 1, 2014 |
Current U.S.
Class: |
205/440 |
Current CPC
Class: |
C25B 3/04 20130101 |
Class at
Publication: |
205/440 |
International
Class: |
C25B 3/04 20060101
C25B003/04; C07C 53/02 20060101 C07C053/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 19, 2013 |
KR |
10-2013-0097982 |
Claims
1. An electrochemical reduction method of carbon dioxide,
comprising: reacting carbon dioxide in a solution condition
containing potassium sulfate.
2. The electrochemical reduction method of claim 1, wherein the
method includes: supplying a solution containing carbon dioxide and
potassium sulfate into a reduction electrode unit in an
electrochemical reactor; supplying a solution containing potassium
sulfate into an oxidation electrode unit in the electrochemical
reactor; and applying a current to the reduction electrode and the
oxidation electrode to reduce carbon dioxide.
3. The electrochemical reduction method of claim 2, wherein the
current ranges from 2 mA/cm.sup.2 to 50 mA/cm.sup.2.
4. The electrochemical reduction method of claim 1, wherein a
concentration of the solution containing potassium sulfate ranges
from 0.1 M to 10 M.
5. The electrochemical reduction method of claim 2, wherein the
reduction electrode includes an amalgam electrode.
6. The electrochemical reduction method of claim 5, wherein the
amalgam electrode includes a dental amalgam.
7. The electrochemical reduction method of claim 6, wherein the
dental amalgam includes Hg of from 35 wt % to 55 wt %, Ag of from
14 wt % to 34 wt %, Sn of from 7 wt % to 17 wt %, Cu of from 4 wt %
to 24 wt %.
8. The electrochemical reduction method of claim 1, wherein a
conversion efficiency of carbon dioxide by the electrochemical
reduction method is 50% or more.
9. The electrochemical reduction method of claim 2, adding a
solution containing KOH is continuously added into the oxidation
electrode unit to control pH.
Description
TECHNICAL FIELD
[0001] The embodiments described herein pertain generally to an
electrochemical reduction method of carbon dioxide under a solution
condition containing potassium sulfate.
BACKGROUND
[0002] Gases affecting the global warming are called greenhouse
games and such greenhouse gases include carbon dioxide, methane,
CFC and so on. According to the announcements reported in 2010, an
emission amount of carbon dioxide over the world was about 33
billion tons, which was an increase of about 45% over the emission
amount in 1990, and Korea ranked the 7.sup.th in the world in the
emission amount of carbon dioxide and the 3.sup.rd in the increase
rate of the amount. Foreign advanced countries have already led to
reduce the emission amount of carbon dioxide by introducing the
emission trading system or the carbon tax system.
[0003] With respect to methods for reducing the emission amount of
carbon dioxide, there are generally capture, storage and conversion
processes. Carbon dioxide capture and storage (CCS) technology
isolates carbon dioxide discharged from big emission sources such
as power, steel, and cement plants and so on from the air, and is a
core technology occupying from 70% to 80% of whole expenses.
Captured carbon dioxide may be stored in the ocean, under the
ground, on the ground surface and others, but the storage in the
ocean may cause a problem in the marine ecosystem, and the storage
on the ground surface is still at the initial technology stage due
to problems in storing places and others. Further, in view of
transportation of captured carbon dioxide, there is a difficulty in
widely commercializing the technology. In light of the foregoing,
the process for conversion of carbon dioxide holds a prevailing
position in both environmental and economic aspects, and can
resolve the aforementioned problems, especially, through an
electrochemical conversion method.
[0004] Conversion of carbon dioxide using electric energy can
convert carbon monoxide, formic acid, methanol, methane and others
into various organic compounds by reacting them through an
electrode reaction under a condition of a room temperature and an
atmospheric pressure depending on types of electrode materials and
reaction conditions. In an electrochemical conversion method, since
potential differences of reduction of carbon dioxide and generation
of hydrogen in an aqueous solution are significantly close to each
other, the reduction of carbon dioxide is interrupted by the
competition of the two reactions. Accordingly, it is necessary to
use an electrode having a large overpotential to the generation of
hydrogen and a catalyst or an electrode surface for selectively
converting only carbon dioxide.
[0005] In recent, researchers have actively studied for formic
acid, and the formic acid is used to keep foods necessary for
livestock breeding fresh and also used in a small amount as a
preservative for foods. Besides, formic acid may be used as a fuel
of a formic acid fuel cell, and the current price of formic acid to
input energy is the highest in other materials that can be subject
to be converted. Formic acid is disadvantageous in that, despite
the tendency for the price of formic acid to have increased each
year, uses of formic acid are still a few. Recently, many
researches on a method that produces formic acid by electrolyzing
carbon dioxide have been conducted (Korean Patent No.
10-468049).
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] In view of the foregoing, the present disclosure provides an
electrochemical reduction method of carbon dioxide using a solution
condition containing potassium sulfate.
[0007] However, the problems sought to be solved by the present
disclosure are not limited to the above description, and other
problems can be dearly understood by those skilled in the art from
the following description.
Means for Solving the Problems
[0008] In a first aspect of the present disclosure provides an
electrochemical reduction method of carbon dioxide, which comprises
reacting carbon dioxide in a solution condition containing
potassium sulfate.
Means for Solving the Problems
[0009] The electrochemical reduction method of carbon dioxide in
accordance with the present disclosure can electrochemically reduce
carbon dioxide in a stable and effective manner to convert it into
formic acid, by converting the carbon dioxide under a solution
condition containing potassium sulfate. Furthermore, since
efficiency of the conversion into formic acid and its economic
efficiency are superior, carbon dioxide can be reconverted into
useful materials at low costs with simultaneously, processing
carbon dioxide so that high added values can be created.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 schematically shows an electrochemical conversion
process of carbon dioxide in accordance with an illustrative
embodiment of the present disclosure.
[0011] FIG. 2 is a flow chart of an electrochemical conversion
process of carbon dioxide under a conventional solution
condition.
[0012] FIG. 3 is a flow chart of an electrochemical conversion
process of carbon dioxide under a solution condition containing
potassium sulfate in accordance with an illustrative embodiment of
the present disclosure.
[0013] FIG. 4A and FIG. 4B show an electro-reduction system in a
laboratory scale under a solution condition containing potassium
sulfate in accordance with an example of the present
disclosure.
[0014] FIG. 5 is a graph showing a potential of a reduction
electrode upon electrolysis of carbon dioxide under a solution
condition containing potassium sulfate in accordance with an
example of the present disclosure.
[0015] FIG. 6 is a graph showing a voltage to an oxidation
electrode of a reduction electrode upon electrolysis of carbon
dioxide under a solution condition containing potassium sulfate in
accordance with an example of the present disclosure.
DETAILED DESCRIPTION
[0016] Hereinafter, embodiments will be described in detail with
reference to the accompanying drawings so that inventive concept
may be readily implemented by those skilled in the art. However, it
is to be noted that the present disclosure is not limited to the
embodiments but can be realized in various other ways. In the
drawings, certain parts not directly relevant to the description
are omitted to enhance the clarity of the drawings, and like
reference numerals denote like parts throughout the whole document
of the present disclosure.
[0017] Throughout the whole document of the present disclosure, the
terms "connected to" or "coupled to" are used to designate a
connection or coupling of one element to another element and
include both a case where an element is "directly connected or
coupled to" another element and a case where an element is
"electronically connected or coupled to" another element via still
another element.
[0018] Throughout the whole document of the present disclosure, the
term "on" that is used to designate a position of one element with
respect to another element includes both a case that the one
element is adjacent to the another element and a case that any
other element exists between these two elements.
[0019] Throughout the whole document of the present disclosure, the
term "comprises or includes" and/or "comprising or including" used
in the document means that one or more other components, steps,
operations, and/or the existence or addition of elements are not
excluded in addition to the described components, steps, operations
and/or elements. Throughout the whole document of the present
disclosure, the terms "about or approximately" or "substantially"
are intended to have meanings close to numerical values or ranges
specified with an allowable error and intended to prevent accurate
or absolute numerical values disclosed for understanding of the
present invention from being illegally or unfairly used by any
unconscionable third party.
[0020] Throughout the whole document of the present disclosure, the
term "step of" does not mean "step for."
[0021] Throughout the whole document of the present disclosure, the
term "combination of" included in Markush type description means
mixture or combination of one or more components, steps, operations
and/or elements selected from a group consisting of components,
steps, operation and/or elements described in Markush type and
thereby means that the disclosure includes one or more components,
steps, operations and/or elements selected from the Markush
group.
[0022] Throughout the whole document of the present disclosure, the
expression "A and/or B" means "A or B, or A and B."
[0023] Hereinafter, illustrative embodiments and Examples of the
present disclosure will be described in detail with reference to
the accompanying drawings. However, the present disclosure may not
be limited to the illustrative embodiments, Examples and
drawings.
[0024] The first aspect of the present disclosure provides an
electrochemical reduction method of carbon dioxide, which comprises
reacting carbon dioxide under a solution condition containing
potassium sulfate.
[0025] In accordance with an illustrative embodiment of the present
disclosure, the electrochemical reduction method of carbon dioxide
may be largely divided into the following three (3) steps:
electrochemical conversion of carbon dioxide, acidification of a
formate salt, and isolation of formic acid, but the present
disclosure may not be limited thereto (FIG. 1). As illustrated in
FIG. 1, the first step converts carbon dioxide into a formate salt
(e.g., HCOOK or HCOONa) through an electrode reaction in an
electrolytic reactor. The second step acidifies the produced
formate salt by adding sulfuric acid (H.sub.2SO.sub.4) or
hydrochloric acid (HCl) to convert the formate salt into formic
acid (HCOOH). After the acidification, the third step isolates the
produced formic acid (HCOOH) through distillation.
[0026] A conventional solution condition containing a bicarbonate
ion (HCO.sub.3.sup.-) has been researched and used the most since
it can maintain high conversion efficiency and perform a pH buffer
action upon electrochemical conversion of carbon dioxide. However,
if the process is actually performed in the bicarbonate ion
condition, it does not result in any economic profits in view of
costs for electric energy to be consumed and prices of solutions.
As illustrated in FIG. 2, in the electrochemical reduction method
of carbon dioxide under the conventional solution condition, a
reduction electrode unit is in a solution condition, in which about
0.5 M KHCO.sub.3 and about 2 M KCl are mixed with each other, and
an oxidation electrode unit is in a solution condition of about 0.5
M KHCO.sub.3. In order to maintain the balance between ions and
materials in the solutions while the electrochemical conversion of
carbon dioxide occurs, transfer of the ions occurs as indicated in
FIG. 2. To be more specific, an oxygen gas and H.sup.+ are
generated by an oxidation reaction of water in the oxidation
electrode unit, but since K.sup.+ cations are the most fluent as a
cation in the solution, K.sup.+ cations move toward the reduction
electrode unit through a cation exchange membrane such that the ion
balance maintained. In the reduction electrode unit, carbon dioxide
consumes H.sup.+ and K.sup.+ by electrochemical reduction to be
converted into a formate salt (HCOOK). Thus, in order to enable
continuous occurrence of the electrochemical reaction in the
oxidation electrode unit and the reduction electrode unit, KOH
should be continuously supplied for the balance of the oxidation
electrode unit, and HCl should be continuously supplied to the
reduction electrode unit. In this case, KCl will be continuously
precipitated in the reduction electrode unit. Therefore, it becomes
a process in which formate salt, KCl, an oxygen gas, and water are
produced and KOH and HCl should be continuously supplied from the
outside.
[0027] As described, since the electrode reaction of carbon dioxide
occurs in a neutral condition, a material obtained from the
conversion is a formate salt, and in order to convert the formate
salt into formic acid, the formate salt should be acidified by
adding HCl or others. In this case, KCl is also discharged as a
by-product of the reaction. The produced formic acid is isolated
and thus obtained from water as a solvent through a distillation or
extraction method.
[0028] As a result of evaluating economic efficiency of a process
that produces about one (1) ton of formic acid through the
above-described process, there is loss of about 425 dollars per
production of about one (1) ton of formic acid, upon considering
the prices of the solutions that should be continuously supplied
from the outside. In addition, the conventional process needs to
further include step of isolating KCl and KHCO.sub.3 which remain
in a solid form together after the distillation, but such isolating
process is very difficult and cannot be thus easily
accomplished.
[0029] For the electrochemical reduction method of carbon dioxide
in accordance with the present disclosure, am illustrated in FIG.
3, both the oxidation electrode unit and the reduction electrode
unit have the potassium sulfate solution condition, and a process
for producing formic acid through an acidification reaction and an
isolating process after the electrode reaction can be
accomplished.
[0030] As illustrated in FIG. 3, oxygen is generated while
producing H.sup.+ in the oxidation electrode unit as a result of
the oxidation reaction of water, and K.sup.+ and H.sup.+ on the
solution move over into the reduction electrode unit through the
cation membrane. In the reduction electrode unit, carbon dioxide is
converted into a formate salt (HCOOK) by an electrode reaction. For
the balance of ions during the process, KOH needs to be
continuously injected into the oxidation reaction unit. In the
acidification reaction of the second step, when two (2) equivalent
weights of formic acid are produced by using sulfuric acid
(H.sub.2SO.sub.4), one (1) equivalent weight of potassium sulfate
is produced. In the third step, formic acid is isolated through
distillation, and potassium sulfate is isolated through
precipitation so that a relatively simple isolating process can be
operated. As a result of evaluating economic efficiency of
converting carbon dioxide into formic acid through the
above-described process, it is identified that the conversion
results in an economic effect of about 1,000 dollars per production
of one (1) ton of formic acid, which is an increase of about 15
times over the conventional solution condition.
[0031] In accordance with an illustrative embodiment of the present
disclosure, the electrochemical reduction method of carbon dioxide
may include, supplying a solution containing carbon dioxide and
potassium sulfate into a reduction electrode unit in an
electrochemical reactor; supplying a solution containing potassium
sulfa into an oxidation electrode unit in the electrochemical
reactor; and applying current to the reduction electrode and the
oxidation electrode to reduce carbon dioxide, but may not be
limited thereto.
[0032] The reduction electrode may contain an amalgam electrode,
but may not be limited thereto. For example, the amalgam electrode
may include dental amalgam, but may not be limited thereto. The
dental amalgam is produced by mixing mercury and amalgam powders
with each other and may include Hg of from about 35 wt % to about
55 wt %, Ag of from about 14 wt % to about 34 wt %, Sn of from
about 7 wt % to about 17 wt %, and Cu of from about 4 wt % to about
24 wt %, but may not be limited thereto. The amalgam powders may be
classified into a low-copper amalgam and a high-copper amalgam
according to an amount of Cu. Since the low-copper amalgam is known
to be relatively easily subject to corrosion, it would be
preferable to use the high-cupper amalgam as a final electrode
material, but the amalgam powders in the present disclosure may not
be limited to the high-copper amalgam. Amalgam is formed by mixing
liquid mercury and an amalgam powders with each other at a rapid
rate by means of an amalgamator, and this process is called an
amalgam setting reaction. For example, ANA 2000 amalgam powders of
Nordiska contains Ag, Sn, and Cu in amounts of about 43.1 wt %,
about 30.8 wt %, and about 26.1 wt %, respectively. A dental
amalgam is made by mixing the amalgam powders with liquid mercury
at a weight ratio of about 55% for the amalgam powders and about
45% for the liquid mercury. For example, a dental amalgam may be
finally produced with a composition of Hg (45 wt %), Ag (24 wt %),
Sn (17 wt %), and Cu (14 wt %). When an amalgam electrode is formed
by using a dental amalgam, the amalgam immediately after its
production is like clay, and thus, can be processed to have a
desired shape.
[0033] In accordance with an illustrative embodiment of the present
disclosure, the amalgam electrode may be formed in various shapes
according to necessity, and for example, but may not be limited
thereto, a rod or a planar shape, but may not be limited thereto.
In addition, the amalgam electrode may further include a copper or
tin electrode on one surface thereof so as to enable the amalgam to
well conduct electricity, but the present disclosure may not be
limited thereto. For example, in case of a rod-shaped amalgam
electrode, after a front part of a copper rod is processed to be a
sharp point, it fits into a Tefron tubing, and the space between
the copper rod and the tubing is filled with dental amalgam. Curing
of the amalgam is completed by about 90% or more after lapse of
about 24 hours from the formation of the amalgam, and the Tefron
tubing may be removed after about 48 hours for complete curing such
that the amalgam can be used as an electrode. The use of the copper
rod enables the amalgam to well conduct electricity, and
simultaneously, the copper rod serves as a support. Further, in
order to prevent a reaction of the copper rod at the time of
electrolysis, a boundary between the amalgam and the copper rod may
be sealed with a Tafron tape and a heat shrinkable tube so that the
copper rod can be prevented from being exposed to a solution, but
may not be limited thereto.
[0034] For example, an amalgam electrode in a planar shape is
formed by pushing amalgam, which has been mixed by an amalgamator,
into a corresponding space of a mold made of acryl, stainless steel
or others and having an appropriate size. In order to make the
surface of the electrode flat, an instrument like a chisel capable
of applying force uniformly to the whole surface may be used. In
addition, for electric connection, conductors in various shapes
like a copper plate may be added to the mold for the production of
the amalgam electrode. The planar amalgam electrode is also used
after curing of the amalgam for at least 24 hours, but the present
disclosure may not be limited thereto.
[0035] In accordance with an illustrative embodiment, the current
may be, for example, from about 2 mA/cm.sup.2 to about 200
mA/cm.sup.2, from about 2 mA/cm.sup.2 to about 180 mA/cm.sup.2,
from about 2 mA/cm.sup.2 to about 160 mA/cm.sup.2, from about 2
mA/cm.sup.2 to about 140 mA/cm.sup.2, from about 2 mA/cm.sup.2 to
about 120 mA/cm.sup.2, from about 2 mA/cm.sup.2 to about 100
mA/cm.sup.2, from about 2 mA/cm.sup.2 to about 80 mA/cm.sup.2, from
about 2 mA/cm.sup.2 to about 60 mA/cm.sup.2, from about 2
mA/cm.sup.2 to about 40 mA/cm.sup.2, from about 2 mA/cm.sup.2 to
about 20 mA/cm.sup.2, from about 2 mA/cm.sup.2 to about 10
mA/cm.sup.2, or from about 2 mA/cm.sup.2 to about 5 mA/cm.sup.2,
but may not be limited thereto.
[0036] In accordance with an illustrative embodiment of the present
disclosure, carbon dioxide can be converted into formic acid by the
electrochemical reduction method of carbon dioxide, and the
conversion current efficiency may be about 50% or more, and for
example, but not be limited thereto, about 60% or more, about 70%
or more, about 50% or more, about 90% or more, about 95% or more,
from about 50% to about 95%, from about 60% to about 95%, from
about 70% to about 95%, from about 50% to about 95%, from about 50%
to about 90%, from about 50% to about 80%, from about 50% to about
70%, or from about 50% to about 60%, but may not be limited
thereto.
[0037] In accordance with an illustrative embodiment of the present
disclosure, a concentration of the solution containing potassium
sulfate may be from about 0.1 M to about 10 M, and for example,
from about 0.1 M to about 7 M, from about 0.1 M to about 5 M, from
about 0.1 M to about 2 M, from about 0.1 M to about 1 M, from about
0.1 M to about 0.5 M, from about 0.5 M to about 10 M, from about
0.5 M to about 7 M, from about 0.5 M to about 5 M, from about 0.5 M
to about 2 M, from about 0.5 M to about 1 M, from about 1 M to
about 10 M, from about 2 M to about 10 M, from about 5 M to about
10 M, or from about 7 M to about 10 M, but may not be limited
thereto.
[0038] In accordance with an illustrative embodiment of the present
disclosure, continuously adding a solution containing KOH to the
oxidation electrode unit to control pH may be included, and for
example, pH may be controlled to be from about 7 to about 8, but
may not be limited thereto.
[0039] Hereinafter, preferable Examples of the present disclosure
are described. However, the Examples are merely illustrative to
facilitate understanding of the present disclosure, and the present
disclosure is not limited to the Examples.
EXAMPLE
Example 1
[0040] Prior to performing an actual process, a basic experiment
for conversion of carbon dioxide in a laboratory scale was
conducted. For the experimental method, a constant current (5
mA/cm.sup.2) was applied, and conversion efficiency was calculated
by a charge amount for an amount of carbon dioxide converted into
formic acid to a whole amount of flowing charge. FIG. 4A shows a
shape of a H-type cell used in the experiment.
[0041] A H-type cell, in which each of the solutions of the
oxidation electrode unit and the reduction electrode unit has a
volume of about 10 mL, was used, and for both the solutions, an
about 0.5 M K.sub.2SO.sub.4 solution was used. A rod-shaped dental
amalgam electrode having an about 3.5 cm.sup.2 area was used as a
reduction electrode, and a platinum electrode was used as an
oxidation electrode. During the electrolysis, the solutions were
uniformly stirred by using a magnetic stirrer, and the produced
formate salt was quantified by using HPLC. In order to maintain pH
to be from about 7 to about 8 during the electrochemical
conversion, about 1 M KOH was gradually added. Efficiency of the
conversion of carbon dioxide into formic acid was calculated from
the amount of flowing charge and the concentration of the produced
formate salt.
[0042] FIG. 5 illustrates a potential value of the reduction
electrode according to the time when the electrolysis was conducted
with the constant current of about 5 mA/cm.sup.2. In this case, the
conversion efficiency was about 80% or more.
Example 2
[0043] A basic experiment for conversion of carbon dioxide in a
laboratory scale was conducted by using a flow cell as shown in
FIG. 4B.
[0044] A flow cell, in which each of the solutions of the oxidation
electrode unit and the reduction electrode unit has a volume of
about 250 mL, was used, and for both the solutions, an about 0.5 M
K.sub.2SO.sub.4 solution was used. A plate-shaped dental amalgam
electrode having an about 10 cm.sup.2 area was used as a reduction
electrode, and a Ti plate having the same size as the reduction
electrode and coated with RuO.sub.2 was used as an oxidation
electrode. The solutions were circulated at about 30 mL/min rate
through a pump during the electrolysis, and in order to maintain
the ion balance of the whole reaction, a KOH solution was properly
injected from the outside into the oxidation electrode unit. The
produced formate salt was quantified by using HPLC. Efficiency of
the conversion of carbon dioxide into formic acid was calculated
from the amount of flowing charge and the concentration of the
produced formate salt.
[0045] FIG. 6 shows a voltage of the reduction electrode to the
oxidation electrode according to time when the electrolysis was
conducted with the static current of about 5 mA/cm.sup.2. In this
case, the conversion efficiency was from about 60% to about 30%. A
pH value for an electrolyte in the reduction electrode unit was
about 6.5 during the electrochemical conversion of carbon dioxide
for about 24 hours, and a pH value of the oxidation electrode unit
was maintained at about 3.0.
Comparative Example 1
[0046] As illustrated in FIG. 2, formic acid was produced by
electrochemically reducing carbon dioxide under a conventional
solution condition containing bicarbonate ion
(HCO.sub.3.sup.-).
[0047] A solution obtained by mixing about 0.5 M KHCO.sub.3 and
about 2 M KCl with each other was used for the reduction electrode
unit, and an about 0.5 M KHCO.sub.3 solution was used for the
oxidation electrode unit. KOH was continuously supplied for the
balance of the oxidation electrode unit, and HCl was continuously
supplied to the reduction electrode unit. During the conversion
process, formate salt, KCl, an oxygen gas, and water were produced.
Since the electrode reaction of carbon dioxide occurs in a neutral
condition, in order to convert the produced formate sag into formic
acid, the formate sag was acidified by adding HCl. In this case,
KCl was produced as a by-product of the reaction. The produced
formic acid was isolated from water as a solvent through a
distillation or extraction method.
[0048] Economic efficiency of the formic acid produced as described
above was evaluated. The evaluation of the economic efficiency was
conducted for production of about one (1) ton of formic acid, and
current efficiency for conversion of carbon dioxide to formic acid
by the electrode reaction was calculated to have been about 80%.
Tables 1 and 2 below provide the results of the evaluation of the
economic efficiency.
TABLE-US-00001 TABLE 1 Consumption Cost according to the Evaluation
of Economic Efficiency under a Bicarbonate Solution Condition
Consumption Value Molecular Consumption (Consumption Materials Mol
Weight (ton) Price (S/ton) * price, S) Oxidation H.sub.2O 1 18 0.4
0 0 Electrode Unit KOH 1 56.1 2.4 900 2,195 Reduction HCl 1 36.5
0.8 350 278 Electrode Unit CO.sub.2 1 44 1.0 0 0 Electricity 80%
5.25 50 262.5 Consumption Acidification HCl 1 36.5 0.8 350 778
Reaction and Distillation/ 100 Extraction/ Extraction Distillation
Operation 150 Cost Total Consumption 3,263 Cost
TABLE-US-00002 TABLE 2 Profit according to the Evaluation of
Economic Efficiency under a Bicarbonate Solution Condition
Production Produced Value Molecular amount (Produced Materials Mol
Weight (ton) Price (S/ton) amount*price, S) Oxidation O.sub.2 0.5
16 0.2 100 17 Electrode Unit H.sub.2O 2 18 0.8 0 0 Reduction KCl 1
74.5 1.6 500 810 Electrode Unit Acidification HCOOH 1 46 1.0 1,000
1,200 Reaction KCl 1 74.5 1.6 500 810 Total Profit 2,837 Difference
2,837 - 3,263 = -426
[0049] According to the above experiment results, while the
electrochemical conversion efficiency of carbon dioxide effectively
occurred with the efficiency of about 80% or more, it was
identified that the process makes a loss of about $426 dollars per
production of about one (1) ton of formic acid in view of the
prices of the solutions that should be supplied from the outside
for the ion balance with the solutions to be used.
Test Example 1
[0050] In accordance with an illustrative embodiment of the present
disclosure, evaluation of economic efficiency of the formic acid
produced according to the electrochemical conversion process of
carbon dioxide as in Examples 1 and 2 above was conducted. The
evaluation was based on electricity consumption, assuming that
current efficiency for the electrochemical conversion of carbon
dioxide is about 60%, and Tables 3 and 4 below provide the
evaluation results.
TABLE-US-00003 TABLE 3 Consumption Cost according to the Evaluation
of Economic Efficiency under a Potassium Sulfate Solution Condition
Consumption Value Molecular Consumption (Consumption Materials Mol
Weight (ton) Price (S/ton) * price, S) Oxidation H.sub.2O 1 18 0.4
0 0 Electrode Unit KOH 1 56.1 1.2 900 1,098 Reduction CO.sub.2 1 44
1.0 0 0 Electrode Unit Electricity 70% 5.25 50 300 Consumption
Extraction and H.sub.2SO.sub.4 0.5 98 1.1 80 85 Distillation
Distillation/ 100 Extraction Operation 150 Cost Total Consumption
1,733 Cost
TABLE-US-00004 TABLE 4 Profit according to the Evaluation of
Economic Efficiency under a Potassium Sulfate Solution Condition
Production Produced Value Molecular amount (Produced Materials Mol
Weight (ton) Price (S/ton) amount*price, S) Oxidation O.sub.2 0.5
16 0.2 100 17 Electrode Unit Reduction H.sub.2O 1 18 0.4 0 0
Electrode Unit Extraction HCOOH 1 46 1.0 12,000 1,200
K.sub.2SO.sub.4 0.5 174.25 1.9 800 1,515 Total Profit 2,733
Difference 2,733 - 1,733 = 1,000
[0051] As seen from the above results, in addition to formic acid,
which is the product of the electrochemical conversion of carbon
dioxide, potassium sulfate produced after the acidification
reaction using sulfuric add also exhibited high economic
efficiency. An economic effect of about $1000 per production of
about one (1) ton of formic acid can be expected, and this effect
is an increase of about 2.5 times over the conventional solution
process.
[0052] The above description of the present disclosure is provided
for the purpose of illustration, and it would be understood by
those skilled in the art that various changes and modifications may
be made without changing technical conception and essential
features of the illustrative embodiments. Thus, it is clear that
the above-described examples are illustrative in all aspects and do
not limit the present disclosure. For example, each component
described to be of a single type can be implemented in a
distributed manner. Likewise, components described to be
distributed can be implemented in a combined manner.
[0053] The scope of the inventive concept is defined by the
following claims and their equivalents rather than by the detailed
description of the present disclosure. It shall be understood that
all modifications and embodiments conceived from the meaning and
scope of the claims and their equivalents are included in the scope
of the inventive concept.
* * * * *